1. Field of Invention
The inventive subject matter relates to an improved method and apparatus for recycling alcohol contaminated with petroleum distillates, including clearing agents, typically encountered in histocytology laboratories, such as xylene and limonene. The method and apparatus leads to recovery of alcohol and clearing agents as well as a reduction of hazardous waste.
2. Description of the Related Art
A natural byproduct of laboratories is the generation of hazardous waste creating a significant added operational cost to the facility. For example, chlorinated solvents are a major contributor to ozone depletion. The Clean Air Act Amendments of 1990 mandated a reduction in the amounts of solvents released into the atmosphere. Because of this mandate, industrial and laboratory costs have been risen significantly.
Although disposal methods, such as incineration, are available, recycling of reagents is preferred since generated waste products are returned to further use and the total volume of hazardous waste that needs to be disposed by other means is reduced. Since alcohol is an important ingredient in a large number of processes. Therefore, either rendering alcohol free of hazardous pollutants for eventual disposal or recycling the alcohol volumes is of critical importance.
Recycling of solvents is widely used in industry as well as in some industrial and academic laboratory settings. Recycling of solvents can be divided into three primary distillation methodologies. The first utilizes a simple distillation unit, which heats the solvent waste to drive off the solvent as a vapor. The remaining waste at the bottom of the still is collected and disposed. The second type of distillation method requires versions of fractional stills, which produces a higher purity of recycled product than that produced using the distillation method. A disadvantage of fractional stills, however, is the relatively high cost involved in their operation, compared to other methods. The third distillation method utilizes thin film evaporation. In this method the solvent is distilled by running a thin film down a heated cylindrical vessel where it is eventually vaporized. Thin film evaporators are typically utilized in high volume processes that are operated on a continuous basis.
Separation of solvents from a liquid mixture is widely conducted in laboratories and industry by distillation. Efficiency of separation is, to a great extent, dependent on the molecular properties of the solvent mixture and the differences in boiling points of the solvents. Simplified distillations have been disclosed. For example U.S. Pat. No. 6,638,397 issued October 2003 to Camiener, et al teaches a simplified distillation process for recovery of solvents that have similar boiling points. Additionally, U.S. Pat. No. 6,497,813 issued December 2002 to Ackerson, et al teaches a method of purifying petroleum products to remove oils and aromatics using phase equilibria.
A common aspect of these systems is that they are effective at recycling alcohol that has not been contaminated by commonly used petroleum distillates, such as xylene and limonene. Currently available systems are capable of retrieving the volume of alcohol not contaminated with these chemicals but leaves a significant volume of alcohol, up to 50%, that is not economically recoverable and, therefore, must be disposed.
Petroleum distillation products, such as xylene and limonene are routinely used as clearing agents in biology laboratories, such as histology facilities or industrial concerns. A need exists for the removal of these products from alcohol with the intention of either recovering the petroleum distillation products or reducing the concentration in the alcohol volumes to permit easier and cheaper disposition of hazardous waste.